Progressively stamped clip-on noise damping shim for friction assembly, and method and apparatus for producing clip-on noise damping shim

ABSTRACT

A noise damping shim for a friction assembly is produced by a pre-slit step and a bend and blank step. The pre-slit step forms pre-slits in a shim material at locations where tabs of a noise damping shim are to be formed. The bend and blank step bends each of the tabs at a bent angle relative to the shim material while simultaneously blanking a shim body from the shim material to produce a noise damping shim having bent tabs extending outwardly from a periphery of the shim body.

FIELD OF THE INVENTION

The present invention relates to a noise damping shim for a frictionassembly, and more specifically, to a progressively stamped clip-onnoise damping shim, and a method and apparatus for producing a clip-onnoise damping shim.

BACKGROUND OF THE INVENTION

A typical brake system uses one or more friction assemblies. A frictionassembly comprises a brake pad having a friction material mounted on abacking plate. A friction assembly is a replaceable element. Forexample, in a typical disc brake, a rotating disc or rotor rotates witha wheel of a vehicle. A pair of opposing friction assemblies, alsoreferred to as brake pads, are composed of a friction surface supportedby a metal backing plate and are positioned on opposite sides of therotor such that both friction materials face to the rotor. Outside thefriction assemblies are a piston and a corresponding caliper,respectively. When the brake is actuated and the piston and caliper areadvanced closer to each other, the friction assemblies are pressedagainst the rotor between the piston and caliper. Thus, the frictionmaterials contact the rotor to provide a stopping frictional force.

Significant forces are involved in applying the friction materials tothe rotor. Due to the relative movement during the engagement of thefriction materials and the rotor, squeal noise can be produced. In orderto reduce the squeal noise, it is known to attach a noise damping shimto the brake pad.

A noise damping shim is typically attached to the backing plate of thebrake pad using pins or staples through holes formed on the backingplate and shim. In this construction, the shim is subject to significantforce between the friction assembly and the piston or caliper pushingthe shim against the brake pad during the braking operation. In order tominimize movements of the shim relative to the brake pad, the pins andholes need to be precisely dimensioned.

In order to attach shim to brake pad, it is known to provide tabs orhooks projecting outwardly from the periphery of a noise damping shim.When the shim is attached to a backing plate, the bent tabs are engagedto the backing plate. This type of friction assembly is advantageous forrequiring fewer operations to attach the shim compared to the frictionassemblies that use pins. However, the provision of the tabs requiresadditional shim material.

It is therefore desirable to provide a noise damping shim and a methodof producing a shim that reduces material, processing, and assemblycosts.

SUMMARY OF THE INVENTION

It is an object of the invention to provide an improved noise dampingshim and shim manufacturing process for a friction assembly thatobviates or mitigates at least one of the disadvantages of existingsystems.

The invention forms pre-slits in a shim material for forming tabs of aclip-on noise damping shim, and bends the tabs at the same time asblanking the shim body from the shim material.

in accordance with an aspect of the present invention, there is provideda noise damping shim for a friction assembly. The shim comprises a shimbody that provides a noise damping function when the friction assemblyis in use, the shim body having opposing surfaces and a peripherybetween the opposing surfaces; and one or more tabs extending outwardlyfrom the periphery of the shim body, each tab having a base sectionintegrally connecting the tab with the shim body, a hook section forengaging with the friction assembly backing plate, and a bent sectionintegrally connecting the base section and the hook section at a bentangle. An intersection between the periphery of the shim body and eachside edge of the base section of each tab forms a sharp corner.

In accordance with another aspect of the invention, there is provided amethod of producing a noise damping shim for a friction assembly. Themethod comprises a pre-slit step of forming pre-slits in a shim materialat locations where tabs of a noise damping shim are to be formed; and abend and blank step of bending each of the tabs at a bent angle relativeto the shim material while simultaneously blanking a shim body from theshim material to produce a noise damping shim having bent tabs extendingoutwardly from a periphery of the shim body.

In accordance with another aspect of the invention, there is provided ashim forming apparatus for producing a noise damping shim for a frictionassembly. The apparatus comprises a pre-slit unit for forming pre-slitsin a shim material at locations where tabs of a noise damping shim areto be formed; and a bend and blank unit for bending each of the tabs ata predetermined angle relative to the shim material while simultaneouslyblanking a shim body from the shim material to produce a noise dampingshim having bent tabs extending outwardly from a periphery of the shimbody.

In accordance with another aspect of the invention, there is provided aprogressive stamping apparatus for producing a noise damping shim for afriction assembly. The apparatus comprises a progressive stamping diethat includes an upper die and a lower die that open and close forstamping. The stamping die defines a pre-slit stage for formingpre-slits in a shim material at locations where tabs of a noise dampingshim are to be formed; and a bend and blank stage for bending each ofthe tabs at a predetermined angle relative to the shim material whilesimultaneously blanking a shim body from the shim material to produce anoise damping shim having bent tabs extending outwardly from a peripheryof the shim body.

This summary of the invention does not necessarily describe all featuresof the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of the invention will become more apparent fromthe following description in which reference is made to the appendeddrawings wherein:

FIG. 1 is a top plan view of a noise damping shim in accordance with anembodiment of the present invention;

FIG. 2 is a side view of around a tab of the noise damping shim;

FIG. 3 is an enlarged perspective view of the tab;

FIG. 4 is a flowchart of a method of producing a noise damping shim inaccordance with an embodiment of the present invention;

FIG. 5 is a schematic view of a shim material during the production ofthe noise damping shim;

FIG. 6 is a block diagram showing a shim forming apparatus for producinga noise damping shim in accordance with an embodiment of the presentapplication;

FIG. 7 is a schematic view of a progressive stamping apparatus forproducing noise damping shims in accordance with an embodiment of thepresent application;

FIG. 8 shows an example of a tab of the noise damping shim; and

FIG. 9 shows an example of a tab of a prior art shim.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring to FIGS. 1 to 3, a noise damping shim 10 according to anembodiment of the present invention is described. This embodimentdescribes a noise damping shim that is suitably clipped on a frictionassembly of a disc brake for an automotive braking system. In adifferent embodiment, a noise damping shim of a different shape may besuitably used for a different type of a friction assembly.

The noise damping shim 10 has a shim body 20 and tabs 30. The noisedamping shim 10 is clipped on a friction assembly (not shown) using thetabs 30 to provide a noise damping function when the friction assemblyis in use. The shim body 20 has a predetermined shape suitable for thefriction assembly. The shim body 20 typically has a generally flatshape.

Tabs 30 extend outwardly from the periphery 22 of the shim body 20.Typically, a number of tabs 30 are provided on a shim body 20 atlocations that are strategically determined to minimize movements of theshim relative to the friction assembly during the use. In thisembodiment, four tabs 30 are provided as shown in FIG. 1. A differentembodiment may have four tabs at different locations, or a fewer or moretabs.

As shown in FIGS. 2 and 3, each tab 30 has a base section 32, a hooksection 34 and a bent section 36. The base section 32 merges into theshim body 20 and integrally connects the tab 30 with the shim body 20.The hook section 34 provides engagement with the friction assembly. Thebent section 36 integrally connects the base section 32 and the hooksection 34 at a bent angle α, as shown in FIG. 2.

The base section 32 extends outwardly from the shim body 20 in the sameplane as the plane of the shim body 20. The base section 32 of the tab30 and the shim body 20 defines an intersection 42 between each sidewall 32 a of the base section 32 and the periphery 22 of the shim body20. The intersection 42 forms a sharp corner, without any radius. Theangle of the sharp corner is typically about 90°±30° and preferablyabout 90°.

There may be a slit 40 formed at the intersection 42. The slit 40extends into the shim body 20 along the side edge 32 a of the basesection 32. The length of the slit 40 extending into the shim body 20from the intersection 42 is short enough for maintaining the strength ofthe tab 30 and long enough to provide good separation of the shimmaterial at the intersection 42 during the blanking of the shim body 20.The length of the slit 40 measured from the intersection 42 to the otherend is typically between about 0 mm to 3 mm. In a different embodiment,the length of the slit may be longer, depending on the hardness and/orthickness of the shim material or other factors.

The bent angle α between the base section 32 and the hook section 34 ofthe tab 30 is smaller than 90° and is determined so that the multipletabs in cooperation allow the nose damping shim 10 to be clipped on thefriction assembly backing plate, and held on the backing plate by thehook sections 34 of the tabs 30 once clipped on. The bent angle α istypically between about 65° to 85°, and preferably about 75°.

The width of the tab 30 is typically about 8 mm to 15 mm, and 9.1 mm inthis embodiment where the shim 10 has a length of about 134 mm and awidth of about 48 mm. The outwardly extending length of the tab 30 fromthe intersection 42 to the bent section 36 is typically about 3 mm to 6mm, and 3.54 mm in this embodiment. The height of the tab 30 as bent atthe angle α is typically 5 mm to 8 mm, and 5.80 mm in this embodiment.The dimensions of each tab may be determined differently, depending onthe type of the friction assembly backing plate on which the noisedamping shim is clipped.

Referring to FIGS. 4 and 5, a method of producing the noise damping shim10 according to an embodiment of the present invention is now described.The method comprises step 80 of forming pre-slits 60 on a shim platematerial plate 50 at the locations where the tabs are to be formed. Eachpre-slit 60 defines the peripheral edge of a tab 30. Each pre-slit 60may also define slits 40 at both ends of the per-slit 60, each slit 40extending from the intersection of the tab 30 and the shim body 20 intothe shim body 20, as shown in FIG. 3.

The next step 82 bends the tabs while simultaneously blanking the shimbody from the shim material 50. Each tab is bent at a predetermined bentangle α relative to the shim material. FIG. 5 shows the holes 70 left inthe shim material 50 after the shim bodies are blanked together withtabs which were pre-slit.

By forming the pre-slits for tabs in the material before blanking, thetabs can be bent at the same time of blanking the shim body. Thiseliminates the need for a secondary operation to bend tabs. As theresult, the overall production speed can be increased, and costassociated with the production can be reduced. Also, by this method, theshim material can be efficiently used as exemplified in FIG. 5, andthus, scrap can be reduced.

FIGS. 6 shows a shim forming apparatus 100 that is suitably used forproducing the noise damping shim 10. The shim forming apparatus 100 hasa pre-slit unit 110 and a bend and blank unit 120. The pre-slit unit 110forms pre-slits 60 on a shim material 50 at the locations where tabs areto be formed for a noise damping shim 10. The bend and blank unit 120has a blanking section 140 with bend sections 130 for each tab. The bendsection 130 and the blank section 140 are actuated simultaneously. Thebend and blank unit 120 typically has multiple bend sections 130, eachcorresponding to each tab. The bend sections 130 bend tabs, each at apredetermined angle α, at the same time when the blank section 140blanks the shim body from the shim material 50. The shim material 50 ispreferably used in the form of a strip and is fed progressively into thetool.

The combination of the “pre-slitting” of tabs in the shim materialbefore blanking and the “simultaneous tab bending and shim blanking”allows production of clip-on noise damping shims in one progressivestamping tool or apparatus with minimal scrap of the shim material.

FIG. 7 schematically shows a cross-sectional view of a progressivestamping die of such a progressive stamping apparatus 200 in accordancewith an embodiment of the present application. The progressive stampingapparatus 200 progressively stamps noise damping shims. The stamping dieof the progressive stamping apparatus 200 has an upper die comprising apunch holder 202, stripper 204 and stripper window 206, and a lower diecomprising a main blanking insert 208. A strip of shim material 50 isfed between the upper die and lower die. The stamping die opens andcloses for stamping by moving the upper die and lower die relative toeach other.

The progressive stamping apparatus 200 has a pre-slit stage 210 and abend and blank stage 220 for progressive stamping.

The pre-slit stage 210 has slitting mechanisms, each provided at alocation that corresponds to a tab to be formed for a noise dampingshim. Each slitting mechanism has a slitting insert 212 provided in themain blanking insert 208. An upper cutting edge of the slitting insert212 protrudes above the upper surface of the main blanking insert 208.The cutting edge has a shape corresponding to the peripheral edge of atab 30. The cutting edge may also further correspond to slits 40extending into the tab body shown in FIG. 3. The slitting insert 212faces an opening in the stripper window 206 for forming a pre-slit 60 inthe shim material 50. In a different embodiment, the pre-slit stage 210may have a slitting mechanism that has a slitting insert with multiplecutting edges for forming multiple pre-slits 60 for multiple tabs.

The bend and blank stage 220 has bending mechanisms 230 and a blankingmechanism 240. Each bending mechanism 230 is provided at a location thatcorresponds to a pre-slit 60 formed by the pre-slit stage 210. Eachbending mechanism 230 has a bending punch insert 232 provided in thepunch holder 202, and a bending cam 234 provided in the main blankinginsert 208. The bending cam 234 faces the bending punch insert 232. Theblanking mechanism 240 has a main punch 242 provided in the punch holder202, and a counter punch 244 provided in the main blanking insert 208.The counter punch 244 faces the main punch 242. The counter punch 244may be spring loaded.

During the operation of the progressive stamping apparatus 200, thestrip of shim material 50 is fed in the progressive stamping apparatus200 in the direction shown with an arrow A in FIG. 7. The shim material50 is progressively advanced for a predetermined distance betweenstamping strokes of the apparatus 220.

In the pre-slit stage 210, during a stamping stroke, as the stamping diecloses, the upper cutting edge of the slitting insert 212 of eachslitting mechanism penetrates the shim material 50 for slitting apre-slit for forming a tab (216) at a section of the shim material 50.

The next progression brings this section of the shim material 50 to thebend and blanking stage 220. During a stamping stroke, in each bendingmechanism 230, as the stamping die closes, the cam 234 is actuated andbends the tab in cooperation with the bending punch insert 232 (236). Atthe same time, the blanking mechanism 240 blanks a shim body by the mainpunch 242 and the counter punch 244 (246).

The progressive stamping apparatus 200 produces a noise damping shimhaving bent tabs, each bent tab having a sharp corner at eachintersection of the tab and the shim body. The noise damping shim mayalso have remaining pre-slit sections extending into the shim body. FIG.8 shows an example of such a noise damping shim, in which the remainingpre-slit sections 40 is visible on the finished shim, and the sharpcorner 42 is formed at the intersection of the shim body and tab 30without no radius. This is clearly contrary to a shim produced by aconventional apparatus, as shown in FIG. 9, in which the intersection ofthe shim body and tab 90 forms a round corner 92 with a large radius,and there is no slit between the shim body and tab 90.

The progressive stamping apparatus 200 allows production of the entirenoise damping shim in a progressive stamping die, which eliminates aneed of an off-line secondary tab bending operation. This results in anincreased shim production speed, elimination of an off-line tab bendingmechanism, and reduction of production costs.

While particular embodiments of the present invention have been shownand described, changes and modifications may be made to such embodimentswithout departing from the scope of the invention. For example, theprogressive stamping apparatus 200 has a slitting insert provided in thelower die, but in a different embodiment, a slitting insert may beprovided in the upper die. The progressive stamping apparatus 200 usesthe bending cam 234. In a different embodiment, a different mechanismmay be used to bend tabs.

1. A noise damping shim for a friction assembly, the shim comprising: ashim body that provides a noise damping function when the frictionassembly is in use, the shim body having opposing surfaces and aperiphery between the opposing surfaces; and one or more tabs extendingoutwardly from the periphery of the shim body, each tab having a basesection integrally connecting the tab with the shim body, a hook sectionfor engaging with the friction assembly backing plate, and a bentsection integrally connecting the base section and the hook section at abent angle, wherein an intersection between the periphery of the shimbody and each side edge of the base section of each tab forms a sharpcorner.
 2. The noise damping shim as claimed in claim 1, wherein anangle of the sharp corner between the periphery of the shim body andeach of the side edges of the base section of each tab is between about60° to 120°.
 3. The noise damping shim as claimed in claim 2, whereinthe angle of the sharp corner between the periphery of the shim body andeach of the side edges of the base section of each tab is about 90°. 4.The noise damping shim as claimed in claim 1, wherein the base sectionof each tab has opposing side edges, and the base section merges intothe shim body such that each side edge of the base section intersectsthe periphery of the shim body with a slit therebetween.
 5. The noisedamping shim as claimed in claim 4, wherein the slit extends into theshim body along the side edge of the base section, a length of the slitextending into the shim body is equal to or shorter than about 3 mm. 6.The noise damping shim as claimed in claim 1, wherein the base sectionof each tab has opposing side edges, and the base section merges intothe shim body such that each side edge of the base section intersectsthe periphery of the shim body without a slit therebetween.
 7. The noisedamping shim as claimed in claim 1, wherein the bent angle between thebase section and the hook section is smaller than 90° so that the nosedamping shim is clipped on the friction assembly.
 8. The noise dampingshim as claimed in claim 7, wherein the bent angle is between about 65°to 85°. 9-20. (canceled)
 21. A progressive stamping apparatus forproducing a noise damping shim for a friction assembly, the apparatuscomprising a progressive stamping die that includes an upper die and alower die that open and close for stamping, the stamping die defining: apre-slit stage for forming pre-slits in a shim material at locationswhere tabs of a noise damping shim are to be formed; and a bend andblank stage for bending each of the tabs at a predetermined anglerelative to the shim material while simultaneously blanking a shim bodyfrom the shim material to produce a noise damping shim having bent tabsextending outwardly from a periphery of the shim body.
 22. Theprogressive stamping apparatus as claimed in claim 21, wherein thepre-slit stage comprises one or more slitting mechanisms, each slittingmechanism is provided at a location that corresponds to a tab to beformed, and each slitting mechanism has an slitting member provided inone of the upper die and the lower die for forming a pre-slit when thestamping die closes.
 23. The progressive stamping apparatus as claimedin claim 22, wherein the slitting member has a cutting edgecorresponding to a peripheral edge of a tab.
 24. The progressivestamping apparatus as claimed in claim 23, wherein the cutting edgefurther corresponds to pre-slit sections extending into the tab body.25. The progressive stamping apparatus as claimed in claim 21, whereinthe bend and blank stage comprises: one or more bending mechanisms, eachbending mechanism being provided at a location that corresponds to apre-slit formed by the pre-slit stage; and a blanking mechanism having apunch and a counter punch for blanking the shim body as the stamping diecloses.
 26. The progressive stamping apparatus as claimed in claim 25,wherein the bend mechanism has a bending cam that is actuated to bend atab as the stamping die closes.